Contesting is all about the ability to listen. Undesired strong signals, even out-of-band, can cause undesired QRM due to overloading receivers. Harmonics that end up in the next higher bands are even worse. With our current coax stub filters we can suppress small frequency-slices (notches), but the majority of the spectrum passes unattenuated. So, we embarked on a project to remove all signals that are outside the bands of interest.
This bandpass filter project aims at serveral goals:
A view of the 6 filters installed at our patch panel. From top to the bottom: Stackmatch/power splitter, hp-filter + W3NQN filter, coax/rotor patch panel.
On the right side our (remote) rotor control cabinet.
Each plot can be blow-up with a click.
It not easy job to to build a good filter. You will need some skills, tools and patience to fulfilll the job!
Needed tools are at least a VNA to trim the coils. Prefferd a spectrum analyser to check the performance.
A work branche to modify the enclosure, to drill the holes and do some metal works.
To get an idea about the cost for a 10 - 80M filter :
If you still want to continue to build your own filter(s), you may look here.
If you decide to buy a set of PCB's, you will get a nice tool to tunee the needed coils for free.
Attenuation per filter in other band(s).
Last update 18-6-2017